


The Devil Will Teach Them

by Cloud (CloudFlower)



Category: Shingeki no Kyojin | Attack on Titan
Genre: Alternate Universe - Demons, Comedy, Demons, Eren's got a brain, M/M, One-Shot, POV Eren, POV Third Person, Psychology, Rated T for language, School, brief mentions of demons trying to eat their students, ereri, excessive use of the fuck word, nobody gets eaten though, platonic, student!eren, teacher!levi
Language: English
Status: Completed
Published: 2016-05-23
Updated: 2016-05-23
Packaged: 2018-06-10 05:30:14
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 5,879
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6941806
Author URL: https://archiveofourown.org/users/CloudFlower/pseuds/Cloud
Summary: <blockquote class="userstuff">
              <p>There's nothing quite like finding out your old professor got exorcised and a new demon -that no one knows anything about- is now teaching the class...and uhhhh you didn't do your homework.</p><p>(Or a fic where Eren and the 104th attend a school that's taught by demons and everyone is hella confused about the very human looking Professor Ackerman)</p>
            </blockquote>





	The Devil Will Teach Them

**Author's Note:**

  * For [Feolkieer](https://archiveofourown.org/users/Feolkieer/gifts).



> prompt given by a friend ([ tumblr](http://noblehumor.com/post/144415839437/prokopetz-cheesedeity-prokopetz)).
> 
> Thank you friend. I'm sorry this sucks.

Eren latched onto Armin’s forearm like it was his sole remaining lifeline as he hung over the fiery depths of hell, flames licking at his feet.

“Please. Please I’m begging you. Let me copy your psychology homework.”

Armin’s eyes instantly filled with pity as he searched his friend’s face for some hint of mirth, something to show that this was a joke, but he was only met with complete sincerity.

Honest to God, Eren wished it were a joke.

See at every other high school, students whine about how their teacher is ‘totally gonna kill them’ or some shit when they don’t do their homework, but for Eren and his friends at Shiganshina, shit like that _actually_ happened. Like all the fucking time! Well they didn’t necessarily get _killed_ per se, but pretty much anything short of that was fair game. Sure, their education was literally out of this world, but when shit happens and your teachers are asshole demons that would rather eat you as a snack than listen to your very legitimate excuses, life can get a little rough. And people can get a little desperate.

Perhaps even desperate enough to try and copy homework even though the ramifications of such an action might cost both parties a few appendages.

The honor code for the school pretty much summed up to, “Don’t cheat or I’ll eat your fucking toes,” but the only reason Eren was even in this rut was from fear of getting his eyes clawed out so he had already resigned himself to losing a few toes.

He hated that fucking bird professor of astronomy so fucking much.

“Eren, we just started the second quarter and you’re already copying homework? Just take the detention.”

Eren’s eyes widened in fear, “No you don’t understand. I heard that they replaced Professor Tapirgor and no one knows anything about the demon that’s replacing him!”

Armin whistled ruefully while the brunet tugged on fistfuls of his own hair trying to figure out what to do. How was he supposed to know that he didn’t have Tapirgor? Hell, if he hadn’t run into Historia and Ymir this morning, he’d have been waltzing into his psych class without a second thought sans homework and then potentially left without any limbs.

Armin gave his friend another worried look before he sighed in defeat.

New teachers were the worst, after all. Because you never knew what the price would be.

At least with Professor Owlgret if you didn’t do your astronomy homework, you knew exactly what was coming to you because he’d been there for at least two centuries.

Like your great great great grandmother knew what was coming to you.

“Look, I know I should’ve done all of my work, but Birdbreath has been on my case all fucking semester! It was either shirk Tapirgor to do Owlgret’s or the other way around and I don’t know about you, but I’d like to take a chance and keep my eyeballs!”

It really wasn’t fair. There was nothing like having a professor recognize your last name on the first day of class and tell you that he had taught you parents’ parents and their parents. And y’know, that all the Jaegers had such beautiful eyes and he hoped this year would finally be the year he got to _taste_ a pair. The damn bird wasn’t going easy on him either. Always assigning him the hardest topic for projects, taking less of his bullshit on papers, and calling on him repeatedly during class. He had come close to failing a few tests, but so far he’d managed to scrape by. That would have been the end of it though.

Most of the demons reserved eating your legs for when you failed their entire course, but the stricter ones narrowed it to failing their tests. And punishments for late homework varied.

So of course Eren Jaeger got stuck with the one professor in the whole damn school that would eat his eyes for _anything_.

“Fine.” Armin hissed quietly, finally relenting. The blonde boy scanned the area, making sure they hadn’t been seen before scurrying down the hall and taking cover in an abandoned supply closet, Eren hot on his heels.

“I swear the things I do for you. If I lose my toes, I’ll make sure everyone knows it was your fault.”

  
“Thank you,” Eren breathed, giving his best friend a relieved smile. He was really fortunate to have Armin around.

~

You could feel the tension in the air as the class waited for the professor to walk in. Rumors had been spreading like wildfire and Eren hadn’t had time to get his friends in the morning psychology class to confirm or deny any of them. Apparently other people had, but no one seemed to have matching stories.

One kid was swearing that his friend had come out of the class bald, while another claimed the professor had a thing for plucking off fingernails just for talking too much.

“Tim said he was the scariest demon he had ever even seen!”

Eren continued to walk past with Armin alongside him, heading for a pair of empty seats towards the back. Eren didn’t really think that how 'scary looking’ the demon was could accurately judge his cruelty or how hard it would be to pass the class. Putting things into perspective, Owlgret looked like a fucking tiny fluffy owl with long heron legs, but he was worst thing that had ever happened to Eren in his life.

“Sit the fuck down and shut up.” The voice wasn’t particularly loud but like the voice of any demon, it resonated easily through the room, bouncing off the walls.

The entire room fell silent with the exception of butts hitting chairs.

All eyes were facing the front of the room, curiosity overwhelming them to see if the rumors were true.

But the professor looked… not normal per se…but…oddly human.

The demon looked _very_ human.

Two legs, two arms that ended in two hands and two feet. The hair falling into his face was black and silky and the thin fingers shuffling through the folders he had just set down lacked talons. The only thing that really set him apart from an average male adult was his less than average height.

But just like Eren had thought, you really couldn't judge a demon based on how they looked. 

When the professor looked up again he eyed the small class with a steely gaze that set everyone on edge. His eyes had this otherworldly grey and blue glow to them and were even more unsettling given how _human_ everything else about him looked. This demon was all the proof that anyone could possibly need to realize that looks were deceiving.

“All right brats, I’m Professor Ackerman and I’m replacing whoever the fuck. But nobody actually gives a shit so lets get started, shall we?” He gave them an incredibly sarcastic smile that was as shiny as it was false. It lasted no longer than a few milliseconds before his face morphed back into the cold scowl he had been wearing before, “Great.”

He returned to sifting through his folder of papers as he continued talking, “And just to state some simple rules that even you cheeky imps should be able to follow: do your fucking homework, don’t fail my tests, and pass this class because I don’t wanna see any of your shitty faces again after this year. Oh, and before I forget, a note on the homework,” the demon looked up once again, eyes locking on Eren’s and the boy felt his entire body freeze, “Make sure you do you _own_ work.”

_He couldn’t possibly…_

Eren’s head was reeling. There was absolutely no way. _How could he know?_

Eren was ninety percent sure that Armin was shitting his pants in the chair next to him, but he just couldn’t wrap his head around how the professor had found them out. They were literally in a fucking supply closet. No one could have possibly seen them.

The professor turned his back to the class, picked up a piece of chalk and dived straight into his lecture. Eren barely had enough time to rip out a notebook and open it to a fresh page.

By the end of class, no one was really sure what had just happened.

 ~

“What the hell? He doesn’t even _look_ like a demon!” 

“I’m so confused. He is though, right?”

 “Well duh. All the teachers are. Aren’t they?”

“Of course he’s a demon. Haven’t you seen his eyes? They could burn right through your fucking soul.”

Eren groaned from his seat at the table, shoving another bite of lunch rather ungracefully into his mouth. 

He really didn’t want to think about that demon, but it was all anyone was talking about. Professor Ackerman this or that. Half the kids were fawning over him and the other half were scared shitless. And Eren wouldn’t have really cared that Professor Ackerman was a hot topic, but the majority of it was complete and utter bullshit. He hadn’t even known about half the shit that apparently went down during _his_ class and he was _fucking there_. Yet there was no chance of even trying to dissuade any of the rumors spreading about the mysterious instructor.

“I heard that one of the students in his afternoon class called him short and he incinerated him on the spot!”

“I heard that too! Nobody even knows where he went, he just vanished!”

Eren’s eyeballs almost popped out of his head he was rolling them so hard. Owlgret would have fucking loved that.

“I do believe that Professor Ackerman is of the supernatural sort, however I just can’t help but remain a bit unconvinced. You see, his biological makeup gives every suggestion of human genes and he has no clear demonic features.”

“Who gives a fuck, nerd? Didn’t you hear? He can make people fucking _disappear_!”

“But doesn’t he have a point? You can’t be a demon and not have any demonic features.”

The crowd burst into a fierce debate. It pretty much ended with the side that was convinced Ackerman was a demon--the more popular opinion--demanding that the kid who had spoken before explain exactly what he had meant. The boy seemed a bit shaken but appeased the crowd by explaining the characteristics that defined demons and how Professor Ackerman wasn’t quite matching up to them. He had everyone’s attention, even Eren’s.

The brunet had been almost completely convinced that Ackerman was from hell an hour ago, but this kid had a point. A lot of things weren’t making sense.

Was Ackerman even a demon?

~ 

The students were even quieter than usual and, considering how scared the majority of the class was of Professor Ackerman to begin with, it was impressive.

All the kids had their eyes attentively on their teacher, yet if anyone had bothered to look around the room they might have noticed that none of them were really paying attention to anything the professor was saying. A few here and there still hid under the guise of taking notes, clutching pencils in pale hands, but their pages were just as snowy-white as everyone else’s. They were all too busy watching. 

When Professor Ackerman leaned to the side to grab the eraser the entire class leaned with him like the floor itself had given an intoxicated lurch. When the instructor leaned up to write above his diagrams that covered the most reachable parts of the white board, the class rose with him, trying to catch a glimpse of _something_.

But it was useless.

“Did you see anything?”

Another tray of food was set down and the same damn question was repeated with no one providing any kind of answer.

No one had seen _anything_.

This _demon_ had no visible horns, no tail hidden in his pants, no third arm strapped to his chest, no excess of legs separated into two pant holes, literally everything about him was human!

“So what? He’s just not a demon after all?”

“Excuse the pun, but no fucking way in hell. I have never been more terrified of any living thing before in my entire existence and I refuse to accept that he’s a human.” 

“Humans can be scary too, dipshit, just look at your own face. I bet you’ve made tons of babies cry.”

“That was so uncalled for!”

“What, you—”

“Ugh! Just shut up and focus! If no one can spot any kind of demonic trait then he’s gotta be a human! But I don’t think a single one of us at this table sincerely believes that that _thing_ is the same species as _us_.”

There were heads bobbing in agreement and Eren certainly wasn’t disagreeing.

He was surprised when Armin tentatively raised his hand. The group of people looked at him with crazed eyes hoping for any kind of insight the distinguishably intelligent boy could give them.

“Well, umm, see, I know we talked about how it might not be visible and that’s why we were looking for a hidden tail or something, but his demonic trait could be even more hidden than we originally thought by being completely internalized. For example, an extra organ that results in him having some kind of incredible ability--like perhaps an extra set of lungs that allow him to hold his breath longer than any human. But there would be no situation to warrant him demonstrating such an ability.”

“So…what you’re saying, Armin…is that he has some demonic trait inside him?”

“Wait! Like what if it was like super good sense of smell or something?”

“Um, relative to humans, all demons have an exceptionally keen sense of smell.”

“Oh.”

“Wait, can all demons hear really well too or is that just Professor Loinwheel?”

“Well most demons possess a keen sense of hearing as well, but it would vary among differen—.”

“But isn’t that something we can actually test? If we can prove that Ackerman has extraordinary hearing then we know for a fact he’s not human, right?" 

There were nods of agreement as everyone processed the new idea. Eyes glanced furtively around the table as each person come to the same conclusion.

Someone would have to say something, either during class or around Professor Ackerman. It would have to be said audibly, but too quiet for the normal ear to pick up at such a distance.

But in order for it to work…someone would have to say something that would actually evoke a reaction from Ackerman.

And the easiest reactions to notice were probably joy, fear, surprise, and anger.

Joy and fear were out of the question. The professor didn’t seem to be capable of smiling and anything that scared Ackerman--enough for him to visibly display signs of fear--was something that Eren didn’t want to think about.

“I say we draw straws to determine who the sacrifice is." 

Eren sighed as he reluctantly accepted that everyone really had come to the same conclusion he had.

  
They’d have to say something to piss off Ackerman.

And pray that the professor was really human after all.

~

“I’m sorry, but I really just can’t do it!”

The entire table groaned.

“You have got to be fucking kidding me. Nac, it’s been three whole fucking days! We’re dying over here!”

“Yeah man. We’re gonna be old and grey by the time you grow a pair of balls.”

“If you want to know so badly then why don’t you do it?”

“Nobody _wants_ to do it, you spineless dumbass! That’s why we drew straws!”

“And don’t even try to say it was unfair or that you didn’t want to be a part of it! We drew straws just like everyone agreed. There was no cheating; everyone picked their own damn straw and you pulled the short one, Nac.”

The boy was completely distraught. Tears were running down his face as he begged someone else to take his place.

Eren sighed. He was rather disgusted by how cowardly Nac was being, but he did his best to keep a neutral expression. He really hated people who agreed to do things and take risks, but when the time came to deliver, backed down. All talk, no action. 

Nac was still blubbering--saying they should have a redraw and that it wasn’t fair.

There was nothing Eren hated more than cowards that couldn’t even admit their own shortcomings. It was probably this pent up resentment that made him say, “I’ll do it.” 

No one seemed to actually know what he was talking about so he said it again, firmer.

"I'll do it."

“Do what?”

“Piss Ackerman off and hope for the best.”

The dam broke.

“What?!”

“You’re such a fucking suicidal bastard! Who the hell volunteers for that kinda shit?”

“Eren fucking Jaeger does, that’s who. Of course you’d volunteer, who else?”

“Is that really fair?”

“Shouldn’t we redraw straws, guys?”

“Hey, if he wants to do then let him.”

“Yeah, it’s better than forcing someone who doesn’t want to.” 

“You think he actually wants to? He’s only volunteering because everyone around here is so fucking chicken!”

“Ya and he’s probably just as sick a’ waitin aroun as the resta us!”

Eren waited for the outbursts to calm down before speaking again. “I’ll do it tomorrow during class.” 

The Nac kid was looking at him like he was his personal savior come down from heaven.

Eren hated it.

~

If Eren had thought the tension had been high on the first day of class, he needed a reality check. He could pretty much hear the air sizzling with static charge as everyone sat on the edge of their chairs. They watched as Eren waited for the perfect moment.

It was about halfway through class and Ackerman had turned to write something on the board so if Eren said it now and Levi called him out it would be purely the result of his hearing. 

A few of his classmates sent him questioning looks, eyes wide with a mixture of worry and curiosity.

He took a deep breath and then opened his mouth to breathe perhaps the most vulgar sentence he had ever come up with in his life. He couldn’t really picture that Professor Ackerman even owned a dog, but hey, it was offensive and that’s all that mattered.

...It was done. 

The room stilled as eyes shifted from Eren to the professor to see if there was any reaction.

But the professor just kept on going. For a second Eren thought that he might have gotten away with it. Game over, Ackerman’s a human, but then the instructor stiffened.

Everyone watched horrorstruck as Professor Ackerman stopped writing midsentence and turned around stiffly to face the class.

His eyes were narrowed into slits and he definitely looked more angry than usual, the line between his brows was even more pronounced as he glared over the sea of students with a deep scowl. His eyes were…searching for something—

  
They stopped directly on Eren.

The brunet had never been more panicked than under the weight of that heavy stare for the second time that year.

“Jaeger.” His voice was like a blast of cold air. He tilted his head slightly, gesturing to the door, “Outside. Now. 

As he stood, he caught a glimpse of several pairs of eyes that were filled with concern. They looked almost a bit guilty. As if they had sentenced Eren to this and they were just now realizing it wasn’t worth it. But Eren had volunteered and he was brave enough to face whatever was coming.

At least he hoped so.

Was it possible to grow back an arm? Maybe. He could probably ask the nurse to use some supernatural healing shit on him, but it would come with a price.

Nac was crying again.

He saw it as Professor Ackerman held the door open, waiting for him to step out before following him and shutting the door behind them.

It really pissed Eren off.

If there was one thing the brunet could say with confidence, it was that he had definitely spared the professor all of Nac’s insufferable sniveling.

“So brat,” Eren turned to look at his instructor who was now standing with his arms crossed just in front of the large wooden door that was now shut, leaving him pretty much alone...With the professor they had just confirmed to truly be a demon. 

“What the fuck was that? And don’t give me any of your bullshit.”

“I’m very sorry, sir.”

“I don’t give a shit if you’re sorry. Stop disrupting my fucking class.”

Eren’s eyes widened. Was that it? He was just in trouble for disrupting? 

“Yes, sir.” He tried to say it as convincingly as possible. If Ackerman didn’t want to take it any further then Eren was more than willing to let the whole thing drop.

“You have detention in my room for a week. Now get your ass back in there.”

The door opened again and his classmates seemed stunned to see him scuttling to his seat looking very much unharmed.

 ~

“Oh my God, Eren, I thought you were a goner for sure!”

“What did he say to you outside? You looked pale as death when you came back in. Did he try to eat you?”

“You’re such a lucky bastard!”

“I can’t believe it! He really is a demon.”

“Speak for yourself, I said he was since the beginning.”

“Yeah, but then you agreed he might not be when we pointed out he didn’t have any demonic traits, you dolt!”

“That doesn’t mean anything! I was still right!”

Eren ignored the squabbling and pulled Armin closer to his side so they could have a relatively private conversation as everyone marveled in the uncovering of Professor Ackerman really being a demon.

“Armin.”

His friend read his thoughts before he could even voice them, “You don’t think it’s true, do you?”

He shook his head, confirming Armin’s words. 

“Why?”

“Because he,” the boy frowned, thinking back to the way Levi had stared at him with his arms crossed, “he didn’t actually hear me. I’m not really sure how he knew it was me, but he had no idea what I had even done. He just told me to stop disrupting class and said I had detention. That was it.”

“So he didn’t mention you saying anything?”

“No. And I’m pretty sure you heard, but I said some pretty insulting things that would definitely warrant my ass getting beaten to a pulp, not thrown in detention.”

Armin nodded distantly.

Eren shrugged. “It’s not the best proof, but I think everyone’s gotten a little carried away with all of this anyway. It doesn’t matter if he’s a human or a demon at this point. Both are capable of cruelty and it doesn’t change the fact that we should strive to pass the class and all the tests. Honestly, it’s probably better if everyone thinks he’s a demon actually.”

“I agree. I think they’ll be less likely to slack off because of some misconception of assumed mercy solely based on species.”

Either way, the professor sure played the part of a devil. 

~

“Here. And you’re not leaving 'til you’re done.”

Eren eyed the cleaning supplies that had been thrust into his hands with suspicion as Professor Ackerman returned to his desk and pulled out work that needed to be graded.

“I don’t know why you’re still standing there like a dumbass that can’t even remember how to take a shit. Get to work.”

It seemed like Eren’s detention was to be spent cleaning the classroom. He wasn’t really sure where to start…or really what needed to be cleaned...so he carefully set the bin down and pulled out bottles one by one, reading what they were for to get an idea of how much cleaning he had to do. It was a lot, but Eren definitely preferred working his arms sore to getting them bitten off any day.

Eren worked quietly and efficiently. It was a bit awkward at first, knowing that Professor Ackerman was right there making sure he didn’t slack off in his cleaning, but Eren soon realized that the man was busy grading papers and didn’t actually give a shit how ungraceful Eren was as he bumbled around the classroom, scrubbing down surfaces and plucking gum off the bottom of chairs.

Professor Ackerman didn’t speak except for the occasional, “I’ll be checking over your work when you’re done brat, if I don’t like it, you can stay here all night cleaning.” And that was fine.

He wasn’t really sure what he had expected his week with the professor after school to be like, but he definitely didn’t mind it too much. It was a bit dull if he was being honest, but, in comparison to what Eren expected from any of his other teachers, it was God-sent. Sure, he had to redo several sections and he was absolutely exhausted by the end of it, but he left the room with all of his limbs intact and plenty of time to get all of his homework done.

~

Eren wasn’t really sure why he had to redo everything that he had done yesterday. What was the point of cleaning the room when there hadn’t even been enough time for more dust to settle on the shelves?

Regardless of how clean the room looked, Eren was still handed the same bucket of cleaning supplies and told to make the room spotless. The boy shrugged and set to work wiping down the desks. He figured he’d just be done way more quickly than yesterday. Which was fantastic.

Unfortunately, the professor also seemed to have less work to do today and spent more of his time watching Eren clean. Which was… a bit unsettling.

While the silence had been vaguely comfortable yesterday, it was near torturous today with Ackerman watching him, eyes glowing and hands clasped below his chin.

Eren’s grip tightened around the broom he had been sweeping with. “Um, sir?”

“What is it, brat?” He sounded rather annoyed that Eren was letting himself be distracted from his cleaning.

“Uhhh, may I ask a question?”

Eren waited for a reply, but the instructor didn’t give any. If it weren’t for the way Professor Ackerman’s eyebrows raised just a touch, Eren would’ve thought he hadn’t been heard at all.

 _Well he’s not saying no_.

“How did you know it was me?”

“Know what was you, brat?” his voice had lost its previous annoyance but was as impassive as ever.

“The…thing in class. The reason why I got detention.” The boy frowned at the floor, unsure of how to even phrase his question without necessarily giving himself away. He wanted to know the truth.

“You’re here because you were disrupting class, Jaeger.”

“But what did I do?” He chose to make his voice more innocent than quizzical. If the professor thought he was being tested he would immediately shut down Eren’s questions. Hopefully if he tried to play the innocent student, while it would probably irk Ackerman, he might be able to confirm his suspicions.

The professor gave an irritated grumble, “Brat, you know exactly what you did.”

Eren let his eyes grow wide, an expression of confusion dawning across his face as he shook his head.

“Don’t look so fucking confused, Jaeger. You had the entire class staring at you and a guilty as hell look on your face, so you can stop the innocent bullshit.”

It was a bit hard not to smile so he quickly said, “Yes, sir.” And turned his back to the teacher, sweeping the floor vigorously as he grinned.

 _Ackerman doesn’t_ know _what I did. He didn’t hear me. He didn’t actually hear anything I said._

~

“You’re human.”

They were the only ones in the room and Eren was a hundred percent sure that the professor had noticed Eren rubbing his cloth on the same square inch of desk space for the last four minutes.

The man glanced up from his work, but only briefly before he seemed to think better of answering Eren and returned to grading.

“It’s true, isn’t it?”

“Did you mean to phrase your first statement as a question or do you simply wish to accuse me of belonging to some random species without any of my input?”

“It wasn’t really a question because I think you’re human, but I want you to confirm it.”

“Why?”

“Why are you dodging the question so much?”

“Because I don’t really see why I should answer it, brat.”

Eren grumbled and tried to return to cleaning, but he just couldn’t end it there. He threw the rag down on the desk and sat on the now, very clean surface that wasn’t even damp anymore, and faced Professor Ackerman’s desk.

“Armin and I talked about it and we decided that it was better for us to let everyone else still think that you’re a demon.” 

This seemed to catch the man’s attention and he put down his paperwork with a sigh, clasping his hands together under his chin once again.

“And who gave you the right to make them believe one way or the other, shitty brat?”

He might get killed for this, but something in the back of his head said that he would be fine so he surged on.

“The day that you gave me detention. I was elected to be the one to test whether you were a human or a demon so now everyone thinks that you’re a demon and I didn’t tell them otherwise.” 

“Oh?”

He nodded, destroying any chance of hiding what had happened that day. 

“Do continue. I’d love to know how your experiment went.”

His grey eyes had a dangerous gleam to them, but Eren pretty much ignored it. He already knew Ackerman was dangerous. All the teachers were.

“You don’t know what I did, do you? You just know that I did something. And that’s why I think you’re human. You’re very perceptive, but you’re not a demon.”

The professor sighed once again and the mask fell off. The danger was replaced with an almost smug attitude.

“Of course I’m a human. It’s really incredible that you idiots are being taught by the sharpest minds in the universe and yet you all still have shit for brains. You can’t even recognize a member of your own species.”

“But I did!” Eren sputtered defensively.

“Tch. Barely.”

Eren bristled instinctively, words already at the tip of his tongue, prepared to fly off at any second, but he swallowed them back.

The professor almost returned to his work, but Eren stopped him once again.

“But you…You wanted us to think that you were a demon, didn’t you?”

“And what makes you say that, shitty brat?”

Eren leisurely folded his hands in his lap, legs dangling freely from the desk. “The way you acted and spoke. But the weird thing is that even though you looked human we just assumed you were a demon. Just like you said, we couldn’t recognize a member of our own species and that seems strange to me.”

The professor studied him for a few minutes. When he spoke his voice didn’t hold that resonating boom it did during class.

“I’m sure you’ve heard of the term 'bias' before in your other classes, but part of psychology is the study of the different types of biases people have.”

Eren leaned forward, as the professor kept speaking.

“We haven’t gotten anywhere close to this topic yet in class, but there’s something called an expectation bias, where even learned psychologists may disregard clear facts simply because they don't correlate with their expectations.” 

“But—”

“I know what you’re thinking, brat, and yes, it is perfectly plausible. People don’t do it on purpose, it’s a _bias._  Many times people are completely unaware that they’ve even skewed the data to match their expectations.”

“So because we expected you to be a demon, you were?”

“Because all of your other teachers are demons, you expected me to be a demon as well and thus disregarded any evidence you had to support me being human. I just didn’t try to stop you.” 

“Oh.” Eren fell silent after that. 

“Oi, brat. You still have to finish cleaning the rest of the room. If you slack off again like this tomorrow, I’m extending your detention another week.”

“Yes, sir!” Eren slid off the desk and promptly returned to work.

And even though Eren continued asking the professor questions every time he stayed to serve his daily detention, Professor Ackerman didn’t extend his punishment. They actually had some pretty interesting discussions about branches of psychology the class hadn’t even gotten to yet, and Eren would have been lying if he said he didn’t find it interesting. Perhaps even more so than when he was sitting in the back row with Armin.

~ 

Just walking into the room brought back memories.

“Oi brat, if I recall correctly you were there when I said I didn’t want to see any of you shitty brats again after you passed the class. Let alone after graduating.”

“Yeah, I guess I was,” Eren replied casually.

The professor threw him a glare as if to say,  _then what the fuck are you doing here?_

“Oh c’mon, how could you not want to see me after making sure I spent all that extra time with you after school cleaning your room?” 

“You wouldn’t have had to stay if you'd just learned to do your own homework and stopped distracting my class.”

Eren hummed, neither confirming nor denying professor Ackerman’s accusation.

“Y’know, speaking of homework, there is one thing I never got to ask you.”

“Well what the hell is stopping you now? You never seemed to shut up with your goddamn questions; I’m shocked you still have one left.”

“Hah. Well, I have to say I was never able to figure out how it was that you knew I copied Armin’s homework on the first day of class. Especially given that you’re human.”

The instructor leaned back casually against his desk, waiting a few moments before responding.

“You know, next to that closet you pulled Armin into, there’s actually a men’s restroom. Hardly anyone knows about it or uses it so it stays relatively clean and I made it something like my own personal bathroom in this shithole. I keep it clean and no one goes in. I just happened to be washing my hands and on my way out I saw you and your blonde friend booking it into the closet. At first I thought it was just two shitty teenagers finding somewhere to make out, but then I heard you two talking and realized that you were copying homework.”

The man had the nerve to shrug at the end, as if something like this was to be expected. As if Eren hadn’t _agonized_ over how it was that Ackerman had known he had cheated.

“That’s…” Eren paused unsure of even the right words.

“That’s bloody fucking ridiculous is what that is!”

Professor Ackerman gave his old student a small smile.

 

**Author's Note:**

> After developing a much more intimate relationship with his old professor, Eren was able to confirm with quite a bit of certainty that yes, every part of Levi Ackerman was in fact human. ;p
> 
> The End
> 
>    
> Thank you for reading!  
> [My Tumblr](http://cloudflowerkami.tumblr.com)


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